Arrangement in an electrical fuse for projectiles

ABSTRACT

An ordnance fuze for projectiles that includes means for providing both a proximity fuse function and an impact fuse function. A fusible wire is included in the device so that both of said functions are available when the fusible wire is intact. External electrical contacts are provided whereby an external voltage can be applied to the fusible wire to melt same and thereby deactivate the proximity fuse function while maintaining the impact fuse function. The fuze can be used either as a proximity fuze or an impact fuze and provides a very simple means for switching between the two functions.

United States Patent 11 1 [H1 3,750,588 Nordgren Aug. 7, 1973 [541 ARRANGEMENT IN AN ELECTRICAL FUSE 3,6i 1,940 10/1971 Hopkins .1 102/702 P FOR PROJECTILES 3,614,782 10/1971 Adrian i, 3,167,018 1/1965 Brunner .1 Inventor: J Lemur! Nordgren. g y. 3,230,478 1/1966 Page 102 701 ux Sweden [73] Assignee: U.S. Philips Corporation, New York, Primary Examiner-8enjamin A. Borchelt N.Y. Assistant Examiner-H. 1. Tudor [22] Filed: y 14' 1971 Att0mey-Frank R. Trifari Appl. No.: 162,506

\ USC [57] ABSTRACT An ordnance fuze for projectiles that includes means for providing both a proximity fuse function and an impact fuse function. A fusible wire is included in the device so that both of said functions are available when the fusible wire is intact. External electrical contacts are provided whereby an external voltage can be applied to the fusible wire to melt same and thereby deactivate the proximity fuse function while maintaining the impact fuse function The fuze can be used either as a proximity fuze or an impact fuze and provides a very simple means for switching between the two functions 11 (flllms, 2 Drawing Figures ARRANGEMENT IN AN ELECTRICAL FUSE FOR PROJECTILES The invention relates to an arrangement in an electrical fuse for projectiles, a so called proximity fuse, comprising a detecting device sensitive to the presence of a target in the vicinity of the projectile and adapted to influence an electrical ignition circuit for initiating an electrical igniter connected to the ignition circuit when the projectile is at a predetermined distance from the targetv The arrangement also includes an impact device comprising at least one impact contact adapted to initiate the said or a separate igniter through a separate ignition circuit when the projectile hits a target. In such a combined fuse comprising both a proximity fuse func' tion and an impact fuse function, the said last function serves as an additional function if the proximity fuse part should not be effective. Furthermore there is usually an auto-destruction device involving automatic initiation of the igniter in the path of the projectile before it has reached the ground, for example, after a certain time interval from the firing, which device is used at fire across the own area.

An object of the invention is to provide a combined fuse which can be used either as a proximity fuse or as an impact fuse, whereby the need for storing different types of fuses will be eliminatedv For this it is required that switching from proximity fuse function to impact fuse function shall be effected in a simple manner immediately before the firing, for example, automatically.

The characteristic for the invention consists in that in such a fuse a fusible wire arranged within the fuse is electrically connected to the detecting device and/or to the said first ignition circuit in such manner that the said devices have their normal function when the wire is uninterrupted, while when the connection through the wire is broken the detecting device or the ignition circuit respectively are rendered inoperative, which wire is connected to contacts accessible from the outside so that by connecting a voltage between the said contacts the fusible wire can be melted off for deactivating the proximity fuse function under maintenance of the impact fuse function. In a suitable embodiment the detecting device has the shape of a high-frequency oscillator coupled with an antenna coil for transmitting a high-frequency signal and receiving signals reflected from objects in the vicinity of the projectile, which signals by being combined with the transmitted signal will give rise to a Doppler signal forming the control signal for the said first ignition circuit, in which case a preferred embodiment of the device according to the invention consists in that one of the contacts for the fusible wire is arranged at the top of the fuse and connected to the wire through the antenna coil, while the second contact is formed by the envelope of the fuse.

Due to the fact that the fusible wire is accessible through a contact arranged at the top of the projectile maximal simplicity and reliability at the switching is achieved, whereby this switching can be carried through also under difficult conditions, for example, in darkness. By simple means the switching can also be made automatic, for example, in a separate device or in the firing tube in successive order as the projectiles are fed into the same. By utilizing as connection lead between the top contact and the fusible wire the antcnna coil there will neither be any unadvantageous effects on the high frequency system, which would occur if a separate connection lead were drawn in vicinity of the antenna coil.

The invention is illustrated in the accompanying drawing, in which;

FIG, 1 shows a circuit diagram for a device according to the invention and FIG. 2 shows as an example how impact contacts arranged near the top of the projectile can be connected backwardly according to the principles of the inven' tion.

In FIG. 1, Use designates an oscillator included in a fuse for a projectile, which oscillator is coupled to an antenna coil L,. The generated high-frequency signal is transmitted via an antenna formed by the coil and the projectile itself. High-frequency signals reflected from objects in the vicinity of the projectile are led via the same antenna back to the oscillator. If there is mutual motion between the projectile and the reflecting ob ject, the oscillation amplitude of the oscillator will vary periodically in rhythm with the change in distance to the object. This variation or so called Doppler signal is derived in a suitable manner by means of a detector D and applied after amplification in an amplifier F to an ignition circuit. The ignition circuit for the Doppler signal comprises, in the example shown, a capacitor C, which is connected to ground through a thyristor 1, controlled by the Doppler signal and also through an igniter l in series with a diode D, so that a series circuit comprising T,, C,, D, and I will be formed. The capacitor is kept charged continuously by means of a charging circuit consisting of two resistors R,, R When the thyristor is ignited under the influence of the Doppler signal, the circuit comprising the capacitor C, and the electrical igniter l in series with diode D, will be closed, whereby the capacitor will be discharged and the discharge current will initiate the igniter I.

Autodcstruction can be obtained by means of a rotary activated switch AD. The switch AD is closed at a certain rotational speed, which is lower than the initial speed. Alternatively autodestruction can be obtained by means of a timing device TP, which makes the same closing as AD after a certain time. According to a further alternative, autodestruction is produced by a pulse generator 'lf'l which delivers a positive pulse to the control electrode of the thyristor T, after a certain time. In all cases the same ignition circuit is activated by the autodestruction as the one which is influenced by the Doppler signal, and the electrical igniter will be initiated in the same manner as described, namely by discharge of the capacitor C,

Furthermore one or more impact contacts are arranged in a separate ignition circuit or in several individual circuits. In FIG. I only one impact contact A, is shown and the ignition circuit for it consists ofa capacitor C in series with the common electrical igniter l. The capacitor C is kept charged by means of a charging circuit consisting of a resistance R;,, the diode D, and the resistor R At impact against a target the contact will be closed, whereby the capacitor C will be discharged through the electrical igniter and initiates the same.

The diode D, serves to block the negative voltage pulse appearing upon the discharge of capacitor C so that capacitor C, will not shunt the pulse. The capacitor C, is suitably larger than the capacitor C,

Both the oscillator and the charging circuits obtain their voltage from a battery connected between the tersilver is connected both to the oscillator and to the ignition circuit for the Doppler signal. The wire is more particularly connected such that the oscillator receives its ground connection through the wire. The connection of the wire to the ignition circuit includes a transistor T which is arranged with its collectoremitter path in parallel with the thyristor T and thus is connected in parallel with the capacitor C and the resistor R Transistor T has its base grounded through the fusible wire W.

The fusible wire can be influenced from outside because one terminal thereof is connected via the antcnna coil L, to a fixed contact K arranged at the top ofthe projectile. The opposite terminal is connected to the envelope H, i.e., to ground.

The operation of the device is as follows.

When the fuse is to operate as a proximity fuse no special measures need be taken. The fusible wire is intact so that the oscillator is grounded, whereby it will start to oscillate when the voltage from the battery appears. The base of transistor T is connected to the same potential as its emitter, whereby it is kept cut-off. The transistor thus shows a high resistance as seen from the junction point between R C whereby the capacitor C will be charged at the appearance of voltage from the battery. At the appearance of a Doppler signal of sufficient size the thyristor T, will be triggered into conduction, whereby the capacitor C, will be discharged and the electrical igniter will be initiated. The impact fuse function is effective and will serve as a back-up function if the proximity fuse function should fail for any reason. Also the autodestruction is effective, if present.

When the fuse is to be switched-over to the impact fuse function only, a voltage of sufficient value is connected between the top contact K and ground. The current flowing through the antenna coil and the fusible wire will melt the wire. The melting of the wire takes place before the firing, whereby during the melting no voltage is present across the oscillator or across the charging circuits. By the melting of the wire the oscillator will lose its ground connection and therefore it cannot oscillate when voltage then is applied to its terminal. At the same time the base of transistor T, loses its ground connection. As a result the transistor T, will be conductive when the voltage from the battery appears, whereby the voltage across thyristor T, will be limited to a maximum of approximately 1 volt. The capacitor C, cannot be charged and both the Doppler circuit and the autodestruction circuit will be inoperative. However, the capacitor C will be charged and the impact fuse function is effective.

In FIG. 2 there is shown an example as to how two impact fuse contacts A A in case these must be placed in the front of the fuse, can be connected to the rear part of the tube in basically the same manner as described for the top contact K. The outer envelopes ofthe contacts A and A forming one electrode in the respective contact are, according to FIG. 2, connected to the connection lead between the top contact K and the antenna coil L,. The envelopes of the contacts will thus contribute to the antenna loading in the proximity fuse together with the top contact K. The fixed counter electrodes in the respective contact, which at impact against a target will come in electrical connection with the envelopes via the movable contact element, are in 5 corresponding manner connected to individual coils L and L respectively, which are arranged together with the primary coupling winding L, and wound in the same groove as winding L on the base ofthe coil. Consequently all elements above the coupling winding will have the same high-frequency potential. The coils L, and L are connected to ground through capacitors C The ignition circuits for the impact fuse contacts, which can be of the same configuration as shown in FIG. I, are then connected to the junction between the windings L and L and the associated capacitors C C Even though the described arrangement with a contact for the fusible wire arranged at the top of the pro jectile is advantageous both from a manufacturing point of view and from a functional point of view, different contact arrangements are possible within the scope of the invention. An example of an alternative contact arrangement is shown on the drawing comprising an insulated contact ring K which is adapted to replace the top contact K. Also in other respects different modifications of the described arrangement are possible within the scope of the invention. Thus it is not necessary to deactivate the oscillator so that it is prevented from generating oscillations at the melting of the fusible wire, but it is sufficient that the ignition circuit for the Doppler signal is blocked. Alternatively the ignition circuit can be operative and the oscillator inoperative, for example, in the described manner, provided that the autodestruction is not present or is deactivated in another manner. Furthermore the electrical connec tion of the fusible wire is not necessarily as shown but any suitable circuit for connecting the fusible wire to the oscillator or the ignition circuit, respectively, which fulfils the described function, can be used. In principle it is also possible to utilize the principles of the invention in proximity fuses having different types of detecting devices, for example, IR-detectors.

I claim:

1. An electrical fuse device for projectiles comprising, an electrical ignition circuit, an electrical igniter connected to the ignition circuit, a detecting device which coupled to the ignition circuit and sensitive to the presence of a target in the vicinity of the projectile to control the electrical ignition circuit for initiating said electrical igniter when the projectile is at a predetermined distance from the target, an impact fuse device including at least one impact fuse contact connected to a separate ignition circuit so as to initiate an igniter through said separate ignition circuit upon impact of the projectile against a target, a fusible wire arranged within the fuse and electrically coupled to the detecting device and the first ignition circuit in a manner such that the detecting device and the ignition circuit will provide their normal function when the wire is intact, but when the wire connection is interrupted one of said devices will be rendered inoperative in a manner to deactivate the proximity fuse function of the device, means connecting the wire to contacts which are available from the outside of the projectile, said contacts being adapted for connection to a source of voltage of a magnitude sufficient to melt the fusible wire thereby eliminating the proximity fuse function while maintaining the impact fuse function of the de vice.

2. A device as claimed in claim 1, further comprising an auto destruction device arranged to automatically initiate the fuse in the path, and means connecting the auto destruction device to said first ignition circuit so that it will be inactivated together with the proximity fuse function if the fusible wire is melted.

3. A device as claimed in claim 1, in which the detecting device comprises a high frequency oscillator which is coupled to an antenna coil for transmitting a highfrequency signal and receiving signals reflected from objects in the vicinity of the projectile, means for combining transmitted and received high-frequency signals to form a Doppler signal which serves as the control signal for said first ignition circuit character ized in that one of the contacts for the fusible wire is connected to the wire via the antenna coil.

4. A device as claimed in claim 3 further comprising means connecting the oscillator to ground through the fusible wire so that when the wire is melted the oscillator ceases to function.

5. A device as claimed in claim 3, in which said first ignition circuit comprises a capacitor connected in a continuous charging circuit, means connecting the capacitor in series with the electrical igniter and a controllable switching element to provide a discharge path for the capacitor via said igniter and switching element, means for coupling the Doppler signal to a control electrode of the switching element so that the switching ele' ment is controlled by the Doppler signal to discharge the capacitor through the electrical igniter, a second switching element connected across the capacitor, and means connecting a terminal of said second switching element to ground through the fusible wire so that in the event the wire is melted the second switching element is brought to a condition of low resistance whereby it will prevent charging of the capacitor.

6. A device as claimed in claim 3 further comprising a second impact fuse contact arranged near the top of the projectile, and means connecting the second contact to the ignition circuit through an individual coil (1,, 1 which is wound together with said first coupling coil.

7. An electrical fuze system for a projectile comprising, means for transmitting to and receiving an RF signal from a target in the vicinity of the projectile, an electrical igniter for the fuze system, ignition circuit means coupled to the igniter to control the operation thereof detection circuit means responsive to a received RF signal and coupled to said ignition circuit means to cause same to operate the igniter when the presence of a target is sensed at a predetermined dis tance from the projectile, a source of DC supply voltage located within the projectile and coupled to said ignition circuit means and said detection circuit means an impact fuse device including an impact contact mounted on the projectile and connected to said ignition circuit means to cause same to operate the igniter upon impact of the projectile with a target, a fusible wire located within the fuze system and electronically coupled to one of said circuit means so that said circuit means will provide its normal function so long as the wire is intact but will be prevented from providing the proximity fuse ignition function when the wire connection is interrupted, and means connecting the fusible wire to contacts accessible from the outside of the projectile, said contacts being adapted to be connected to a source of voltage capable of melting the fusible wire thereby deactivating the proximity fuse function while maintaining the impact fuse function of the system.

8. A system as claimed in claim 7 wherein said transmitting and receiving means includes an antenna coil which connects the fusible wire to one of said accessible contacts.

9. A system as claimed in claim 8 wherein said detection circuit means includes a high frequency oscillator coupled to the antenna coil and means for combining the transmitted and received high frequency RF signals to form a doppler control signal for operating the ignition circuit means.

10. A system as claimed in claim 8 wherein said fusible means is coupled to the detection circuit means so as to provide a ground connection therefor.

H. A system as claimed in claim 9 comprising means for connecting the oscillator to ground via the fusible wire so that an interruption in the wire deactivates the oscillator. 

1. An electrical fuse device for projectiles comprising, an electrical ignition circuit, an electrical igniter connected to the ignition circuit, a detecting device which coupled to the ignition circuit and sensitive to the presence of a target in the vicinity of the projectile to control the electrical ignition circuit for initiating said electrical igniter when the projectile is at a predetermined distance from the target, an impact fuse device including at least one impact fuse contact connected to a separate ignition circuit so as to initiate an igniter through said separate ignition circuit a fusible wire arranged within the fuse and electrically coupled to the detecting device and the first ignition circuit in a manner such that the detecting device and the ignition circuit will provide their normal function when the wire is intact, but when the wire connection is interrupted one of said devices will be rendered inoperative in a manner to deactivate the proximity fuse function of the device, means connecting the wire to contacts which are available from the outside of the projectile, said contacts being adapted for connection to a source of voltage of a magnitude sufficient to melt the fusible wire thereby eliminating the proximity fuse function while maintaining the impact fuse function of the device.
 2. A device as claimed in claim 1, further comprising an auto destruction device arranged to automatically initiatE the fuse in the path, and means connecting the auto destruction device to said first ignition circuit so that it will be inactivated together with the proximity fuse function if the fusible wire is melted.
 3. A device as claimed in claim 1, in which the detecting device comprises a high frequency oscillator which is coupled to an antenna coil for transmitting a high-frequency signal and receiving signals reflected from objects in the vicinity of the projectile, means for combining transmitted and received high-frequency signals to form a Doppler signal which serves as the control signal for said first ignition circuit characterized in that one of the contacts for the fusible wire is connected to the wire via the antenna coil.
 4. A device as claimed in claim 3 further comprising means connecting the oscillator to ground through the fusible wire so that when the wire is melted the oscillator is unable to function.
 5. A device as claimed in claim 3, in which said first ignition circuit comprises a capacitor connected in a continuous charging circuit, means connecting the capacitor in series with the electrical igniter and a controllable switching element to provide a discharge path for the capacitor via said igniter and switching element, means for coupling the Doppler signal to a control electrode of the switching element so that the switching element is controlled by the Doppler signal to discharge the capacitor through the electrical igniter, a second switching element connected across the capacitor, and means connecting a terminal of said second switching element to ground through the fusible wire so that in the event the wire is melted the second switching element is brought to a condition of low resistance whereby it will prevent charging of the capacitor.
 6. A device as claimed in claim 3 further comprising a second impact fuse contact arranged near the top of the projectile, and means connecting the second contact to the ignition circuit through an individual coil (L2, L3) which is wound together with said first coupling coil.
 7. An electrical fuze system for a projectile comprising, means for transmitting to and receiving an RF signal from a target in the vicinity of the projectile, an electrical igniter for the fuze system, ignition circuit means coupled to the igniter to control the operation thereof, detection circuit means responsive to a received RF signal and coupled to said ignition circuit means to cause same to operate the igniter when the presence of a target is sensed at a predetermined distance from the projectile, a source of DC supply voltage located within the projectile and coupled to said ignition circuit means and said detection circuit means, an impact fuse device including an impact contact mounted on the projectile and connected to said ignition circuit means to cause same to operate the igniter upon impact of the projectile with a target, a fusible wire located within the fuze system and electrically coupled to one of said circuit means so that said circuit means will provide its normal function so long as the wire is intact but will be prevented from providing the proximity fuse ignition function when the wire connection is interrupted, and means connecting the fusible wire to contacts accessible from the outside of the projectile, said contacts being adapted to be connected to a source of voltage capable of melting the fusible wire thereby deactivating the proximity fuse function while maintaining the impact fuse function of the system.
 8. A system as claimed in claim 7 wherein said transmitting and receiving means includes an antenna coil which connects the fusible wire to one of said accessible contacts.
 9. A system as claimed in claim 8 wherein said detection circuit means includes a high frequency oscillator coupled to the antenna coil and means for combining the transmitted and received high frequency RF signals to form a doppler control signal for operating the ignition circuit means.
 10. A system as claimed in claim 8 wherein said fusible wire is coupled to the detection circuit means so as to provide a ground connection therefor.
 11. A system as claimed in claim 9 comprising means for connecting the oscillator to ground via the fusible wire so that an interruption in the wire deactivates the oscillator. 